Power supply units in electronic appliances often perform a multiplicity of tasks. They usually have to deliver a plurality of voltages for the various components and have sensors and drivers for peripheral devices. In this context, the instantaneous power requirement of the various loads in the electronic appliance may, in an unfavourable instance, exceed the average load by a multiple. A power supply unit which also keeps such load peaks under control would be overproportioned for normal operation, however.
In mains-independent, battery-operated appliances such as mobile telephones and portable computers (e.g. personal digital assistants (PDAs)), on the other hand, the size of the appliance needs to be minimized. Dimensioning the power supply unit for all conceivable load scenarios is therefore not acceptable. Rather, it is the task of intelligent control software to minimize the load peaks on the power supply unit through clever load distribution over the various loads, for example as a result of turning on at different times.
The quality of the control software therefore determines the necessary dimensioning of the power supply unit and thus also influences the size of the appliance. It is therefore becoming increasingly important to develop the control software, which generally runs on a microcontroller.
In a first phase of the development of the control software, the behaviour of the power supply unit and of the connected peripheral devices (arising currents and voltages, quantities of heat etc.) in various load scenarios is usually simulated. In this context, the underlying model includes empirically known characteristics of the power supply unit and of the connected peripheral devices, such as the heat dissipation behaviour and the power requirement.
In a second phase, the simulated load scenarios are verified experimentally by test passes. If an error situation arises in this case, for example in the form of overloading of the power supply unit or of the connected peripheral devices as the result of limit values being exceeded for particular critical parameters such as current, voltage or temperature, then in many cases an interrupt signal is transmitted by the power supply unit to the microcontroller on which the control software is running, which aborts the test pass. This results in a multiplicity of test passes needing to be carried out, with the cause of the abortion of a test pass, the subsequent error recognition and elimination and then a fresh test pass respectively needing to be carried out iteratively.